1. Field of Invention
The present invention relates to a method and apparatus for light curing dental light-curing resins so as to improve the properties such as the surface property of the resultant cured resins.
2. Prior Art
In recent years, light-curing resins have been employed in the preparation of dental laboratory products (prostheses) for use in dentures, removable space maintainers, removable orthodontic appliances, crowns and bridges, and the like.
The light-curing resins are easier to handle and faster to polymerize than the conventional self-curing resins or heat-curing resins which require a powder and solution to be mixed with each other. It has a further advantage that the resulting product includes only a few air bubbles and has good properties since it has been in advance prepared in a one-paste form.
However, the conventional light-curing denture base resins are treated in such a manner that the resin paste is finger-pressed and fixed onto a stone cast and then light-cured. This process is time-consuming and requires much skill to obtain an air bubble-free surface with uniform thickness.
In addition, although the air bubbles within the resin paste are invisible with a naked eye, minute air bubbles have often been found arisen on the surface contacted with the stone cast when light-cured under normal pressure, because the resin paste is detached from the surface of the stone cast due to polymerization and contraction.
Accordingly, the resin prosthesis thus obtained has been deteriorated with respect to the surface property of the contacted surface with the stone cast, and its mechanical resistance is unsatisfactory.
Moreover, in the process of light curing of crown and bridge-veneering resins wherein the resin paste is built up, using an instrument, on an opaque resin surface applied to the metal surface of a facing, and then light-cured under normal pressure, contraction will take place at a laminated part between the opaque resin surface and the resin paste before the completion of the light curing of crown and bridge-veneering resins. As a result, a satisfactory adhesion strength can not be obtained.
When the resulting prosthesis is used, said laminated part will break inside the mouth. Application of adhesive primer, for example, has been tried for preventing such break, but it has proven to be an unsatisfactory solution.
Furthermore, the conventional light-curing resins tend to leave more unpolymerized layer than heat-curing resins because they are polymerized and cured at a room temperature. Thus, the cured product has poor mechanical resistance, and absorbs much water. Accordingly, it is highly soluble and lacks long-term durability inside the mouth.